1. Field of the Invention
The manufacture of nonwoven webs has matured into a substantial industry. A wide variety of processes for making such webs has been developed ranging from papermaking to spinning of polymers with air guns or mechanical drawing. A wide variety of uses also has been developed for such webs including, (1) single use items such as surgical drapes, (2) multiple use products such as wiping cloths, (3) durable fabrics for the manufacture of carpeting and the like and (4) components in disposable products such as diapers and sanitary napkins. The present invention is directed to methods and apparatus for forming nonwoven webs, particularly those having a basis weight generally in the range of from 0.1 to 10 oz/yd.sup.2, by spinning thermoplastic polymers. Such webs find uses in the manufacture of disposable products such as diaper liners and sanitary napkin wraps. In the heavier basis weights, the webs may even be used for more demanding applications such as carpet backing, tent fabric, and the like.
In general, the present invention is directed to nonwoven webs formed by spinning filaments of thermoplastic polymers, drawing them aerodynamically to a desired denier and collecting the filaments on a porous surface in an overlapping fashion to form a web which, when bonded, provides a material having sufficient strength for many applications and which can be further treated for additional applications. More particularly, the present invention is directed to such a method and apparatus which makes nonwoven webs by forming a row or rows of filaments extending for the full machine width and drawing the filaments in a full machine wide nozzle.
2. Description of the Prior Art
It is well-known to produce nonwoven webs from thermoplastic materials by extruding the thermoplastic material through a spinnerette and drawing the extruded material into filaments by eduction to form a random web on a collecting surface.
Eductive drawing occurs where discrete jets are formed which entrain a surrounding fluid in turbulent flow. In general, eductive devices require separate sources of fluid, usually air, and produce drawing by kinetic energy. For example, U.S. Pat. No. 3,692,618 to Dorschner et al describes such a process and apparatus for carrying it out employing a series of eductive guns through which bundles of filaments are drawn by very high speed air requiring a high pressure source. An attempt is then made to spread or oscillate the bundles to generate overlapping loops in a web which then can be bonded and employed in applications for nonwovens. Drawbacks to this process and apparatus include:
(1) the necessity for a high pressure air supply;
(2) the educting of low pressure air causing highly turbulent flow, and, therefore, filament intertwining;
(3) the difficulty of getting all the eductors to produce filaments having the same characteristics;
(4) plugging of the eductors by broken filaments; and
(5) non-uniform basis weight profiles resulting from poor bundle spreading or variations in degree of filament entanglement.
British Pat. No. 1,285,381 to Fukada et al describes a similar eductor process and apparatus which, while employing a full machine width drawing chamber, uses exit nozzles that are subject to the same problems of plugging, rethreading, and turbulent mixing encountered with the guns of the previously described patent. This patent also discloses a noneductive arrangement having a segmented configuration. U.S. Pat. No. 3,802,817 to Matsuki et al also describes a full width eductor device and method which, while avoiding the exit nozzle plate of Fukada et al, still requires high pressures and is limited to lower speeds for practical operation. U.S. Pat. No. 4,064,605 to Akiyama et al similarly describes apparatus employing high speed air jet drafting.